When contacts are brought together to effect an electrical interconnection to interconnect the components of computer systems and the like, it becomes important that low resistance, stable signal paths are established. To this end, the circuits of components, as for example, those carried by printed circuit boards, typically include contacts which are plated with precious metal finishes such as gold or, in some instances, thin or alloys thereof, which are brought together with sufficient normal force to eliminate effects of surface-carried debris, insulating oxidation products, or other substances contaminating such contact surfaces. As a general rule, finishes, including gold alloys, have been employed to minimize the development of oxides which interfere with current flow, and in the case of the lower cost applications where tin or alloys of tin are used, relatively high forces are of necessity employed. For example, in gold finish systems, the forces may be on the order of 80 to 100 grams, while with tin finishes, the required normal force can range from 250 grams to more than 300 grams per contact. A classic improvement employed with both types of finishes is to provide a mechanism which wipes the contacts together under pressure, to penetrate contaminating films and clear debris from the path of contract. An even more refined technique is to use wipe upon closure of contacts with a backwipe wherein the contacts wind up in an area previously wiped clean by an initial engagement.
The foregoing techniques are well known and widely used throughout the interconnection industry wherein the contacts, connectors, and the like are relatively substantial in size and few in number. When applied to the developing high density connectors involving not just dozens of contacts, but hundreds of contacts per connector, located on centers of 0.050 inches and substantially less, to result in closure forces of 50 lbs. or more, the conventional structures for providing wipe and/or backwipe are inadequate.
Accordingly, it is an object of the invention to provide, with respect to a high density, high contact count connector, a simple structure for providing wipe and backwipe between rows of contacts. It is a further object to provide a high density, high contact count connector for interconnecting the contacts of printed circuit boards such as those on daughter boards to those on mother boards in a highly reliable wiping engagement. It is a still further object of the invention to provide a contact system having wipe and backwipe which can be automatically achieved through a particular cam/motor structure, including a shape memory alloy (SMA), thermally responsive motor.